Biological Bases Of Behaviour

PHYSIOLOGY OF NERVOUS SYSTEM (PSY0610)

Introduction to Personal Reflections

  • Common introductory questions posed to the students:

    • What’s your name, and where are you from?

    • Why did you choose psychology?

    • What’s one fun fact about yourself?

    • If you could have dinner with any psychologist (alive or dead), who would it be and why?

    • What’s one thing about psychology that fascinates you?

    • If you could read minds for a day, whose mind would you choose and why?

    • What’s your favorite TV show, movie, or book with a psychological theme?

    • If you could study the psychology of any animal, which would it be and why?

    • What’s one word you’d use to describe yourself, and why?

Historical Perspectives on Behavior Control

The Heart or The Brain?

  • Opening Query: What controls our behavior—the heart or the brain?

  • A rhetorical stance suggesting the heart does not control behavior, indicating a leaning towards brain-centered explanations.

Aristotle's Theory (384-322 BCE)

  • The Heart-Centered View:

    • The heart was considered the control center of the body.

    • While the brain had a minor role, the heart was viewed as:

    • The seat of the soul

    • The source of behavior

    • The center of consciousness

  • Key Arguments from "On the Parts of Animals":

    • The heart generates body heat, controls circulation, and directs vital functions.

Observations Leading to Aristotle’s Cardio-Centric Hypothesis

  • Dissection Observations:

    • Primitive animals displayed movement and sensation without a brain, leading to the belief that the brain was irrelevant for these functions.

  • Key Assumptions:

    • The heart controls sensation and movement.

    • The movement of body parts depended heavily on the heart and associated sinews (tendons).

The Role of Pneuma in Aristotle’s Logic

  • Pneuma (Breath):

    • Thought to serve as a messenger traveling through blood vessels to produce sensations.

    • The heart was viewed as generating heat, essential for life and directing various vital functions.

  • Legacy:

    • While incorrect, Aristotle's hypothesis underscored the importance of anatomy in understanding behavior, laying groundwork for future physiological studies.

Philosophical Reflections on Education

  • Aristotle's Quote:

    • "Educating the mind without educating the heart is no education at all."

Hippocrates' Brain-Centric View (c. 460–370 BCE)

  • The Brain as the Center of Human Experience:

    • Hippocrates was an early advocate emphasizing the brain's role in controlling thoughts and emotions.

    • Key Quote:

    • “From the brain, and the brain only, arise our pleasures, joys, laughter… as well as our sorrows, pains, griefs, and tears.”

  • Functions Attributed to the Brain:

    • Critical functions such as thinking, seeing, and distinguishing between good and bad, as well as emotional regulation.

Brain Health and Mental States according to Hippocrates

  • Acknowledged the brain's condition as a determinant of behavior and emotions.

  • Unhealthy States (e.g., hot, cold, moist, dry):

    • Result in madness, fear, sleeplessness, anxiety, and behavioral mistakes.

  • Holistic Thinking:

    • Emphasized the link between brain health and overall well-being, attributing psychological and physiological symptoms to brain function.

Brain Facts and Composition

Key Facts About the Brain

  • All parts of the brain are used; the myth that "we only use 10% of our brain" is false:

    • We utilize 100% of our brain.

  • Physical Attributes:

    • Average weight: ~1.5 kg.

    • Composition:

    • 60% fat

    • 40% water, protein, carbohydrates, and salts.

Structure and Function of the Brain

  • Contains an estimated 100 billion neurons, along with blood vessels, nerves, and support cells (glial cells).

  • Functions of Supporting Cells:

    • Supply nutrients to neurons.

    • Remove foreign bodies to maintain function.

  • Neural Communication:

    • Neurons and supporting cells work in groups, which coordinate brain functions.

  • Cell Variability:

    • Neurons differ in size and shape based on their location.

Brain Facts: True or False Challenge

  • Game Rules:

    • Teams of students decide if statements about the brain are true or false over 15 seconds.

    • Correct answers earn points, and bonus points for explanations.

True/False Statements Examples

  • Your brain is mostly made of muscle. (False)

  • Your brain uses 20% of your body's energy. (True)

  • The brain can't feel pain. (True)

  • The left brain is creative, right brain is logical. (False)

  • Your brain keeps working during sleep. (True)

  • The brain is the fattiest organ. (True)

  • Neurons transmit signals up to 268 mph. (True)

  • Familiar faces are processed simultaneously by your brain. (True)

  • Brain activity is identical whether imagining an action or performing it. (True)

The Central Nervous System (CNS)

Key Components of the CNS

  • Brain: Control center for bodily functions and responses.

  • Spinal Cord:

    • Connects the brain to the peripheral nerves.

    • A long, thin bundle of nerve fibers extending from brain's base to the lower back; cauda equina (horse's tail) at its end.

Functions of the CNS

  • Spinal Cord Functions:

    • Manages simple reflexes (e.g., withdrawing from pain).

    • Transmits messages between brain and body.

  • Brain Functions:

    • Controls various body activities.

    • Processes external events and responds accordingly.

The Nervous System Overview

  • The nervous system contains four key components.

The Peripheral Nervous System (PNS)

Key Features of the PNS

  • Definition: Network of nerves connecting the CNS to the rest of the body.

  • Components: Nerves from glands, sense organs, and muscles.

  • Location: Exists outside the brain and spinal cord.

Functions of the PNS

  • Information Relay:

    • Receives signals from sense organs and transmits sensory information to the brain.

  • Response Coordination:

    • Sends signals from the brain to muscles, enabling reflex actions (e.g., pulling away from heat).

  • Direct Link to CNS:

    • PNS nerves are directly linked to CNS, ensuring communication.

Autonomic Nervous System

Key Functions

  • Regulates internal organs (heart, stomach, lungs, intestines); manages involuntary responses such as blood vessel adjustments and heart rate changes.

  • Operates without conscious control, maintaining essential bodily functions automatically (e.g., heart rate increase during exercise).

Somatic Nervous System

Key Functions

  • Regulates voluntary movements; connects the brain to motor neurons in skeletal muscles.

  • Facilitates conscious control over actions such as walking or writing (e.g., picking up a pen).

Sympathetic vs. Parasympathetic Nervous System

Sympathetic Nervous System

  • Function: Prepares body for action in stressful situations.

  • Key Features:

    • Increases heart rate and breathing.

    • Dilates pupils.

    • Redirects blood flow to muscles; inhibits digestion.

  • Example: Body’s preparation for fight or flight in threatening situations.

Parasympathetic Nervous System

  • Function: Calms the body and conserves energy after activity.

  • Key Features:

    • Slows heart rate and breathing.

    • Constricts pupils; stimulates digestion.

  • Example: Focuses on digesting food after eating.

Box Breathing Exercise

  • A technique to regulate breath consciously, enhancing relaxation.

Cranial Nerves and Their Importance

Purpose of Cranial Nerves

  • Cranial nerves carry information between the brain and body parts, facilitating essential functions such as vision, smell, hearing, and movement.

Cranial Nerves vs. Spinal Nerves

  • Cranial Nerves:

    • Emerge from the brain and brainstem; connect to the head and neck for sensory and motor information.

    • Essential for senses and facial movements.

  • Spinal Nerves:

    • Emerge from the spinal cord; transmit information between the spinal cord and the rest of the body.

    • Control movement and relay sensory information to the brain.

The 12 Cranial Nerves

Mnemonic for Names

  • Mnemonic: "Oh Once One Takes The Anatomy Final, Very Good Vacations Start Happening."

    • Helps in memorizing cranial nerves:

    • 1. Olfactory (I)

    • 2. Optic (II)

    • 3. Oculomotor (III)

    • 4. Trochlear (IV)

    • 5. Trigeminal (V)

    • 6. Abducens (VI)

    • 7. Facial (VII)

    • 8. Vestibulocochlear (VIII)

    • 9. Glossopharyngeal (IX)

    1. Vagus (X)

    1. Accessory (XI)

    1. Hypoglossal (XII)

Functions of the 12 Cranial Nerves

  1. Olfactory Nerve (I): Responsible for sense of smell.

  2. Optic Nerve (II): Component of the visual pathway; connects the eye to the brain.

  3. Oculomotor Nerve (III): Controls eye movements and pupil dilation.

  4. Trochlear Nerve (IV): Innervates muscles that direct gaze downwards.

  5. Trigeminal Nerve (V): Sensory nerve of the face with branches mediating various facial sensations.

  6. Abducens Nerve (VI): Regulates muscle that pulls the eye laterally.

  7. Facial Nerve (VII): Facilitates facial expressions, tear secretion, and salivation.

  8. Vestibulocochlear Nerve (VIII): Maintains physical equilibrium and sensory information for hearing.

  9. Glossopharyngeal Nerve (IX): Involved in taste and saliva control.

  10. Vagus Nerve (X): Manages multiple organs including the heart; regulates heart rate and digestive functions.

  11. Accessory Nerve (XI): Sends fibers to neck muscles allowing rotation of shoulder blades.

  12. Hypoglossal Nerve (XII): Responsible for tongue movement, essential for swallowing.

The Neuron

Key Concept

  • Neurons communicate via action potentials (electrical impulses).

Definition of Action Potential

  • An action potential is a brief electrical charge that travels along a neuron, enabling signal transmission, induced by rapid ion exchange (sodium and potassium) across the membrane.

Types of Neurons

  1. Spontaneously Active Neurons:

    • Continuously generate action potentials.

    • Information coded by changes in firing rates (akin to a constantly active radio).

  2. Trigger-Dependent Neurons:

    • Normally inactive; fire only when stimulated (like a switch).

    • Return to resting state post-activation.

Neuron Components

Membrane

  • Acts as a covering for the neuron, facilitating communication by allowing selective entry and exit of materials.

Cell Body (Soma)

  • Central part housing the neuron’s nucleus; surrounded by extracellular and intracellular fluid.

  • The large nucleus distinguishes neurons from other cells.

Axons and Dendrites Extensibility

  • Dendrites: Numerous, branched structures that receive electrical signals.

  • Axons: Single axon that transmits signals to other neurons, differing in length.

The Synapse

  • Connection point where communication occurs between neurons:

    • Axons exit cell body at the axon hillock; ends at terminal buttons.

    • In CNS, synapses link neurons; in PNS, may connect to muscle cells for movement control.

Neurotransmitters

Definition

  • Neurotransmitters are chemicals released from presynaptic terminal buttons at the synapse that influence postsynaptic neuron activity.

Key Functions

  • Act as messengers enabling signal transmission across the synaptic cleft.

Types of Neurotransmitter Effects

  1. Excitatory Effects:

    • Increase likelihood of neuron firing (e.g., norepinephrine).

    • Comparable to pressing an accelerator in a vehicle.

  2. Inhibitory Effects:

    • Decrease likelihood of firing (e.g., GABA).

    • Similar to pressing the brake of a vehicle.

Example Process of Synaptic Transmission

  1. An action potential reaches the presynaptic terminal.

  2. Neurotransmitters are released into the synaptic cleft.

  3. Neurotransmitters bind to receptors on postsynaptic neurons, influencing responses based on neurotransmitter-receptor interaction.

Neurotransmitter Types and Functions

  1. Adrenaline: Elevates heart rate and blood flow; associated with the fight-or-flight response.

  2. Noradrenaline: Influences attention and action responses; enhances blood flow by contracting blood vessels.

  3. Dopamine: Linked to pleasure and reward; motivates repeated behaviors leading to release.

  4. Serotonin: Affects mood and regulates sleep cycles; influenced by exercise and lighting conditions.

  5. GABA: Calms the CNS nerves; higher levels aid in focus, while low levels may increase anxiety.

  6. Acetylcholine: Involved in memory and learning; activates muscle action and influences attentiveness.

  7. Glutamate: Most prevalent neurotransmitter; vital for learning and memory formation.

  8. Endorphins: Induces feelings of euphoria and well-being; reduces pain following physical exertion.

Neurotransmitter Match Game Example Statements

  • Sarah feels pleasure after a challenging task: Dopamine.

  • John's racing thoughts impact his sleep: GABA.

  • Maria feels energized after exercising: Norepinephrine.

  • Tom feels peaceful post-meditation: Serotonin.

  • Jake smoothly plays piano from memory: Acetylcholine.

  • Rachel feels a natural high after exercise: Endorphins.

  • Sarah feels overwhelming love holding her newborn: Oxytocin.

The Endocrine System and Hormones

Definition of the Endocrine System

  • A network of glands that produce and release hormones into the bloodstream, working alongside the nervous system for regulatory purposes.

Main Functions of Hormones

  • Body Regulation:

    • Controls metabolism, manages growth and development, regulates reproduction, and maintains bodily balance.

  • Mental and Emotional Impact:

    • Influences mood; manages stress and affects behavior; controls sleep patterns.

Key Hormones and Their Functions

  1. Thyroid Hormone: Regulates energy, metabolism, temperature, memory, heart rate, and immune function.

  2. Growth Hormone: Vital for energy, metabolism, bones/muscles, and repair processes.

  3. Cortisol/DHEA: Manages body's stress response.

  4. Testosterone: Present in both genders; relates to energy, mood, libido, and muscle upkeep.

  5. Estrogen: Executes over 400 functions, controls hot flashes, supports bone density, influences memory, collagen, and mood.

  6. Progesterone: Aids in sleep regulation, anxiety reduction, and brain calmness; protects the uterus.